1. Field of Invention
The invention described herein relates to suspension mechanism used to support and suspend the weight of small, manually manipulated power tools.
2. Description of Prior Art
Mechanisms used to support and suspend small, manually manipulated power tools are provided in several forms. One design, commonly referred to as a tool balancer, consists of a cable wound around a reel which is connected to an adjustable, flat, wound spring which resists the cable's withdrawal from the reel. The free end of the cable is attached to the tool, and the reel is attached to a support means above the work area. The objective is to provide a weightless condition for the tool, wherein an operator may move the tool to a workpiece and altemately up and out of the way of a workpiece to enable a workpiece to be moved in the case of a conveyor line, or to facilitate other operations to be preformed on a workpiece, with relative ease as compared to an unsuspended tool. Another design, less common, but the most simplistic in structure, is a cable attached at one end to the power tool and the other end to a counterweight with an intermediary pulley or pulleys to direct the cable appropriately. Finally, some designs utilize articulated arms linked in a parallelogram or other arrangements in an effort to maintain the tool's angular relationship to the workpiece at varying heights and lateral locations. These mechanisms use either coiled springs which may be tension-adjusted or air cylinders with adjustable pressure regulators to provide the countering force to support the power tool. Power tools vary considerably in weight so it is necessary to have some degree of adjustability. All of the aforementioned designs have merit in the function of counterbalancing a power tool's weight and reducing the necessary effort by the operator to move the tool to the subject workpiece, and to position the tool in a location above and out of the way of the work area. In many applications of power tools, however, a commonly downward, axial force is necessary to perform the desired work, especially in the cases of screwdriving and drilling. The function of the discussed suspension mechanism necessitate that the operator of the power tool supply all of the required downward force. Furthermore, in actual practice, suspension mechanisms are often adjusted to the subject power tool, in order that the tool will refract away from the workpiece when released by the operator. This condition necessitates an even greater amount of downward pressure to by provided by the human operator. The continual repeated application of axial force by the operator results in fatigue, exposure and susceptibility to a variety of cumulative disorders and repetitive motion injuries. The power tool itself, however, possesses a fixed mount of mass which, if utilized, could provide all or part of the required axial force. The utilization of the mass, to be beneficial, could occur only during the actual work cycle of the power tool, so that at all other times, the power tool would by suspended. It would be a great advantage to an operator if a limited, adjustable amount of tension relief could be provided from the suspension mechanism at the instant the tool is actuated, and then revert to the original suspended condition when the work cycle is completed. A device of this type would undoubtedly result in less effort being spent and would consequently result in a reduction in hand, wrist, arm, and elbow injuries, which are commonplace among operators performing this type of work. A hypothetical scenario is a size ten wood screw being installed into door frames at the rate of 5,000 per day. The application requires an axial force of approximately five pound& to drive the screw into the wood. The weight of the tool is three pound&. An additional one pound negative force is created by the suspension device. Utilizing a tension relieving suspension mechanism would provide four of the required five pound& of force to drive the screw. In the course of one workday, a net savings of twenty thousand pound& of effort would be realized by the operator of the power tool in this example. Furthermore, common applications require lateral movements of the power tool to reach various locations of the subject workpiece. Quite often, the suspension mechanism is rigidly mounted above the workpiece and consequently does not follow the power tool laterally through its movements resulting in lateral resistance to movement of the tool. This causes more effort to by expended by the operator and less accurate positioning and performance from the power tool. A tension relief device which is activated at the moment the tool is actuated would greatly improve the use of the power tool and eliminate the lateral force against the desired position of the power tool and thereby greatly reduce fatigue in the power tool operator.